Field of the Invention
The present invention relates to a method of producing a compound having a colorant structure suitable for a pigment dispersant, a pigment dispersant containing the compound, a pigment composition containing the pigment dispersant, and a pigment dispersion and a toner each containing the pigment composition.
Description of the Related Art
The dispersion of a pigment having a small particle diameter in a medium such as an organic solvent or a molten resin is liable to be insufficient because a cohesive force between the particles of the pigment tends to be strong. Accordingly, the use of a dispersant for dispersing the pigment together with the pigment has been proposed for improving the dispersibility of the pigment.
A dispersant obtained by bonding, to a terminal of a polymer that imparts dispersibility in a medium, a compound having a high affinity for a pigment has heretofore been used as a dispersant having high dispersibility. For example, Japanese Patent Application Laid-Open No. 2012-077297 discloses an example in which a dispersant obtained by bonding, to a terminal of a polymer obtained by radical polymerization involving using a thiol-based transfer agent, a colorant compound having a high affinity for a pigment is used for improving the dispersibility of the pigment in toner, and a method of producing the dispersant.
As described above, various dispersants have been proposed in toners of respective colors such as yellow, magenta, cyan, and black colors in order to improve the dispersibility of a pigment in a toner particle.
Japanese Patent Application Laid-Open No. 2012-067285 discloses an example in which a compound having a colorant skeleton structure is used as a dispersant for improving the dispersibility of an azo-based pigment in a yellow toner, and a method of producing the compound. Japanese Patent Application Laid-Open No. 2006-030760 discloses that a specific polyester-based dispersant is used for improving the dispersibility of a magenta pigment in a magenta toner. Japanese Patent Application Laid-Open No. H03-113462 discloses that a polymer containing sodium styrene sulfonate as a monomer unit is used as a dispersant for improving the dispersibility of a phthalocyanine pigment in a cyan toner. Japanese Patent Application Laid-Open No. H06-148927 discloses that a copolymer formed of a styrene-based monomer and an acrylic acid ester-based (or methacrylic acid ester-based) monomer is used as a dispersant for improving the dispersibility of carbon black in a black toner.